Open source scientific bottle roller

Proprietary bottle rolling systems automate some laboratory applications, however, their high costs limit accessibility. This study provides designs of an open source bottle roller that is compatible with distributed digital manufacturing using 3-D printed parts and readily-available commercial components. The experimental results show that the open source bottle roller can be fabricated for CAD$210 (about USD$150) in materials, which is 86% less expensive than the most affordable proprietary bottle roller on the market. The design, however, is more robust with enhanced capabilities. The design can be adapted to the user’s needs, but is already compatible with incubators with a low profile (dimensions 50 cm x46 cm x8.8 cm) and capable of being operated at elevated temperatures. The systems can be adjusted to revolves from 1 to 200 RPM, exceeding the rotational speed of most commercial systems. The open source bottle roller as tested has a capacity greater than 1.2 kg and can roll twelve 100 mL bottles simultaneously. Validation testing showed that it can operate for days at 80 RPM without human intervention or monitoring for days at both room temperature and elevated temperatures (50 °C). Future work includes adapting the designs for different sizes and for different fabrication techniques to further reduce costs and increase flexibility.


Hardware in context
A scientific bottle roller is used to rotate bottles at a set speed ranging from 1 revolution per minute (RPM) up to 80 RPM [1].Bottle rollers are used in a range of scientific research areas such as cell cultivation [2,3], sediment leaching [5], gold particulate separation [6], chemical blending [7], drying [8], and many other applications outside of the lab such as mixing essential oils or bituminous mixtures [9].Although commercial bottle rolling systems automate some of these laboratory applications, their costs limit accessibility as the retail price of a simple single-layer bottle roller costs CAD$1540 (US $1136.97)[10] and those that are used in incubators can cost over CAD$2910 (US$2148.44)[11].The large costs of proprietary scientific bottle rollers summarized in Table 1 limit accessibility in the scientific community.It should be noted that the CAD$ to US$ exchange rate used was about 1.355.
One approach to reducing research equipment costs is to use decentralized production of free and open source hardware (FOSH) [12,13].The FOSH approach can reduce costs [14,15], enable customization and increase control for scientists [13,[15][16][17].This is largely due to the development of open source digital manufacturing technologies such as the self-replicating rapid prototyper (RepRap) 3-D printer [18][19][20].In this open hardware model [21,22] designs are shared for free and then transformed to physical products through digital manufacturing.A review of the recent FOSH literature found scientific FOSH material costs had an average savings of 87% compared to equivalent or lesser proprietary tools [17].These economic savings increased slightly to 89% for those that used open-source electronics like Arduino technology [23], 92% for those that implemented RepRap-class 3-D printing, and 94% with both [17].When scientists build their own hardware [22,24] using parametric FOSH [21,25], it allows for high-quality bespoke research equipment [12,[26][27][28].
The FOSH approach has been applied to chemical mixing in several ways such as: i) an open source 3-D printed nutating mixer [29], ii) rotator mixer and shaker [30], iii) orbital shaker [31], iv) stirring [32] and v) a shake table [33].Open source chemical mixing has also been used at the micro-scale for microfluidic devices [34] as well as for reactionware [35] using a wide variety of readily available chemically compatible feedstocks [36].In addition, open source alternatives are available for pharmaceutical applications [37], and incubation via the Incubot for long-term live cell imaging [38].Bottle rolling, however, has not yet been open sourced using a design that can be readily manufactured using a digital distribution model.
This study aims to overcome this limitation by reducing the cost of bottle rollers using the open hardware approach and distributed digital manufacturing.Specifically, this study provides the designs for an open source bottle roller that is a less expensive alternative to commercial bottle rolling systems, while also increasing the capacity of the bottle roller to allow for fewer bottle rolling systems to be used to complete a larger task.The open source bottle roller is manufactured using 3-D printed parts for custom mechanical parts and readily-available components for the power supply, rollers, bearings, and speed controller.

Hardware description
The open-source bottle roller can be printedon any thermoplastic materials extrusion-based 3-D printer, but to overcome commercial limitations, the main components of the device are fabricated using a RepRap-class fused filament 3-D printer.Furthermore, the electronic parts, rollers, bearings, and speed controller are provided from readily available components in the local markets.The open source bottle roller is fully customizable and allows the user to increase the capacity of bottles on a larger scale.Testing and validation are provided to compare the quality of the open source bottle roller with the available commercial ones, and a comparison in price is made to show the economic advantage of the open-source one with commercial peers.The features of the open source bottle roller include: Low-cost chemical mixing for laboratory purposes Customizable design based on the user's needs Compatible with incubators with a low profile (dimensions 50 cmx46 cmx8.8 cm) Revolves 1 to 200 RPM, while the maximum speed of most commercial systems is 80 RPM Operational in an incubator at elevated temperatures (50 °C) Holds 12 bottles of 100 mL simultaneously.(Capacity greater than 1.2 kgs)

Design files summary
All files are at https://osf.io/ps57u/and released under GNU General Public License (GPL) 3.0 for documentation and CERN OHL-S v2 for hardware.The DOI for the repository is https://doi.org/10.17605/OSF.IO/PS57U and the registration is https://doi.org/10.17605/OSF.IO/5ZRT3 The design file information is summarized in Table 2.
File 1 represents the axis.This part connects the gear to the pipe (Fig. 1).
In design file 2, the belts are shown.These belts connect the gears together to transfer the motor rotation to the pipes (Fig. 2).These belts and the gears are designed and customized based on the device's size and replacing them with the readily available belts in the market is not recommended.Moreover, the quality of the belts can be changed by adjusting the infill percentage in the slicer settings.It should ne noted that the tension on the belts can be adjusted to the users wishes as the belts themselves can be customized and 3-D printed using flexible filament like NinjaFlex or similar.
In design file 3 gear 1 is shown.The gear is designed based on standard relationship between Pitch Diameter, center Distance, and belt Pitch Length [42] (Fig. 3).
The gear 2 is shown in design file 4. The gears are designed differently to easily accommodate the belts and reduce friction between them (Fig. 4).
The shaft goes inside the horizontal hole, and it is held in place by inserting two screws in the vertical holes (Fig. 5).
Since the main body is separated into 8 plates and walls in order to fit the print beds of most desktop 3-D printers, some connectors are needed to connect the plates together.Design file 6 represents these connectors (Fig. 6).
The walls that are parallel to the PVC pipes are shown in Fig. 7.
The outer plates are meant to connect the gears to the pipes.The holes are designed based on the diameter of the bearings (Fig. 8).
The reinforcing bars that are shown in Fig. 9 are designed to keeps the main body from shaking while in operation (Fig. 9).Design file 16 represents the roller mount that should be glued to the PVC pipes.The pipes are connected to the axis and then the gears by theses roller mounts (Fig. 10).
The spacer parts that are shown in Fig. 11 should be located between the roller mount and the axis to enable a proper distance between the roller mount and the bearings.
The motor box keeps the motor and the coupler held in place Fig. 12.
The cover parts in file 19 and file 20 are designed to cover the gears and belts in order to prevent the operator's fingers from getting pinched in them.The printed parts are shown in (Fig. 13 and Fig. 14).
File 21 and File 22 represent the wire covers.Since there is a possibility of liquid spills from the bottles, these covers are designed to prevent the short circuit and reduce safety issues (Fig. 15).
The CAD file for the assembly of the bottle roller parts is represented by Design File 23.For further clarification, Fig. 16 displays the names of the different parts.

Bill of materials summary
The overall design is based on the principle of maximizing strength and service life; thus, all components are designed to have maximum redundancy.Belts were selected as the primary transmission method because chains can cause additional wear and tear on the gears, whereas belts can be easily replaced as they are 3-D printable..In a similar way, the electrical components are selected to be as simple as possible to ensure reliability, so a DC motor and PWM controller are chosen as the power source and speed controller.In addition, the design heavily relies on screws to achieve maximum link strength between printed components.In the aspect of performance, the finished prototype has five rollers to ensure enough room twelve 100 mL bottles to be mixed simultaneously.The motor allows the system to run at the range from 1 RPM to 200 RPM, and the power percentage of the motor can be monitored through the screen on the PWM controller.

Build instructions
The first step for building the open source bottle roller is to 3-D print the parts listed in Table 2 using the STL files, which can be found on the OSF repository.The printing parameters are summarized in Table 4..The main parts and belts were 3-D   printed using PETG and TPU filaments, respectively.PETG was selected for the main parts due to their required strength, while TPU was chosen for the belts for its flexibility.Although the parts can be printed with any compatible 3-D printer, we used the open-source Lulzbot Taz 6 RepRap-class 3-D printer to produce the main parts, and the Lulzbot Sidekick 289 RepRap-class 3-D printer to print the belts, as this allowed for reduced costs.
Next, the other parts from Table 3 must be acquired.The assembling steps are as follows: 1. Acquire all components.2. Cut five sections of the PVC pipe according to Fig. 17.The cut does not need to be highly precise.
3. Use epoxy glue to connect the Roller Mounts to the PVC pipes (Fig. 18).4. Insert the ball bearings inside the Outer Plates holes (Fig. 19). 5. Bolt the half connectors on the Outer Plates (Fig. 20).6. Bolt Reinforce Bars on the Half Connectors (Fig. 21).7. Bolt walls together Fig. 22. 8. Screw the walls to the Outer Plate-1 and Outer Plate-2 (Fig. 23).9. Insert the Axis, Spacer, and PVC pipe in the ball bearings of Outer Plate-1 and Outer Plate-2 and repeat this step for 5 pipes based on Fig. 24.10.Screw the Outer Plate-3 and Outer Plate-4 on the walls (Fig. 25).Moreover, the key notes for the pipes assembly is shown in Fig. 26.11.Insert the Gear, the spacer, and PVC pipes in the ball bearings of Outer plate-3 and Outer plate-4 and repeat the step for all pipes with every other Gear (Gear-1 and Gear-2) (Fig. 27).12. Assemble the electronic components according to the electrical diagram (Fig. 28).13.Insert the motor into the Motor Box and attach them to the Outer Plate-3 (Fig. 29).14.Insert the Belts as shown in Fig. 30.15.Add the covers and electronic parts to the system and finish the assembling Fig. 31.The operation instruction is as following: 1. Plug in the 12 V power supply.
2. Push the button to start the system.
3. Use the knob to adjust the power output to control the motor speed.4. when the user wants to power it off or temporarily stop the operation, reverse the steps 1-3.

Safety
There are several safety hazards that should be considered while working with the open source bottle roller.First, the bottle must be tightly sealed before putting on the bottle roller in case of the liquid spill onto the electronic part to cause       a shortcut and potential electric shock.Secondly, the assembly of electronic components may require soldering, and users must follow the safety instructions during the soldering process to prevent injury.Furthermore, in order to prevent fingers from getting caught under the rollers, the operator should ensure that the speed is set to zero RPM and turn off the device using the speed controller.

Validation and characterization
In this study, the performance of the open source bottle roller design was evaluated by comparing it to commercially available options.For this purpose, the information on the specifications and performance were collected as are provided in Table 1.The variables that will be investigated are: 1) the ability to maintain the appropriate speed that is required for the bottle roller to be effective over the duration of the desired amount of time at room temperature, and 2) the bottle roller ability to maintain constant speed while maintaining structural integrity in an oven at 50 °C.The capital cost is reduced to CAD$210, which is 86% less expensive than the most affordable commercial bottle roller shown in Table 1.Capability of rolling 12 bottles filled with 100 mL water for at least 48 h without failure in room temperature at 80 RPM speed.Although the motor became slightly warm after several days of operation, it functioned safely without raising any concerns about causing injury during use or failure.Ability to operate for 24 h at elevated temperatures (50 °C) without failure.
The bottles roll smoothly on the PVC pipes.To enhance the friction between the bottles and the pipes for applications with heavier masses, the pipes can be sanded or have rubber added to create a rougher/higher surface friction surface.Since the open-source bottle roller is customizable, it can accommodate different sizes of bottles by using PVC pipes with various dimensions.The device includes multiple belts that can be easily removed when the user needs to rotate fewer bottles.By removing belts, the user can reduce the number of pipes that roll, optimizing the device's performance for their specific application.

Future work
The open source bottle roller was designed to be manufactured by most desktop 3-D printers.This asset, however, can be a limitation as because of the printer bed size being smaller than the device, the main body of the bottle roller is separated into eight pieces, which significantly impacts the structural strength.The connectors and reinforcement bars are designed to overcome this limitation by connecting these pieces together, but they result in the excess of printed parts, a slight increase in the height of the system and added costs for connectors.There are several open source approaches to solving this issue.First, a large format open source 3-D printer could be used to print the entire structural frame in a single print.If the large format printer was also a waste plastic fused granular fabrication (FGF)-based 3-D printer (cartesian [54], delta [55], or hang printer [56,57]) the costs of the system could be reduced further by about 10% as recycled PETG particles could be used  instead of filament.For example, the bottle roller could be fabricated by waste plastic PET water bottles [58].Moreover, by selecting a higher melting point 3-D printable polymer like polycarbonate (PC) even higher temperature operation may be possible [59].Another potential solution to this design limitation is to utilize open-source laser cutting or CNC milling [60] to cut the four sides of the bottle roller on a plastic sheet.Further the plastic sheets could be fabricated in an open source hot press from recycled plastic as well [61].This way, the bottle roller can be held in place and the connectors and reinforcement bars can be eliminated and ensure overall strength and stability.In addition, to reduce the purchased components the PVC pipes can be replaced by 3-D printed pipes or extrusion molded pipes from an open source recyclebot [62][63][64][65][66].Moreover, the bottle roller is customizable to be used in different scale applications.The smaller version can be obtained using PVC pipes with smaller diameter.It should be pointed out that the same percentile cost savings could be had by using either filament from an open-source recyclebot or small-scale FGF [67,68].In this regard, changing the dimensions of the provided designs can be helpful.Also, the user can make the bigger version through adding outer plates.The other design that can be useful and adapted easily from the current design for some applications is the stacked version that consist of some bottle rollers on top of each other.This would be helpful for scaling bottle rolling applications to greater production volumes.The bottle roller can also be used for non-cylindrical components or specialty vessels.To do this a 3-D printed component can be fashioned to hold these non-optimal vessels.To illustrate this Fig.32 shows a 3-D printable holder for a microcentrifuge tube, which can then be used on the open source bottle roller.Similar strategies can be used for many microcentrifuge tubes or other types or shapes of containers.

Fig. 23 .
Fig. 23.Screwing the walls to the Outer Plates.

Table 2
Design file information.

Table 3
The bill of material list of hardware components to be purchased.

Table 3
(continued) *Tooling cost is not included.Tools including handsaw, wrench, screwdrivers, and soldering devices are needed during the assembly.